About one in four pregnancies ends in miscarriage. Yet doctors and parents learn the reason why only about half the time.

A few clinical research centers have opened around the country in recent years to help find explanations when pregnancies repeatedly don’t succeed. The centers also study new treatments they hope will help patients boost the chances of a successful pregnancy the next time around.

Just over half of miscarriages occur when a fetus has too many or too few chromosomes from the time of fertilization, doctors say. Most women in this situation go on to have a healthy baby in a future pregnancy. It’s the rest of them that stump doctors.

The Program for Early and Recurrent Pregnancy Loss, or Pearl, provides clinical services to women who have had multiple miscarriages for reasons that aren’t clear. An estimated 5% of couples experience recurring miscarriages. Two other centers affiliated with large institutions also conduct clinical research on miscarriages, including at Stanford University and the University of Illinois at Chicago. The centers might conduct genetic testing, look for hidden infections or hunt for mysterious immune disorders, among other techniques.

Shedding light on the causes and potential treatments after a miscarriage also gives people an emotional boost. “So often after miscarriage women and couples blame themselves. If you can tell a woman this was the molecular basis for your miscarriage, it had nothing to do with what you did, that gives huge relief to the patient,” says Zev Williams, director of the Pearl program, located at Albert Einstein College of Medicine and Montefiore Health System in New York City.